In this chapter, I argue that the local paths of reception of proportionality by French and English lawyers in the field of the convention are shaped by local patterns of cultural change. In the monist and rationalist French system, proportionality and European human rights standards have been received as already inherent in domestic concepts and methods. In contrast, English dualism and analytical formalism long impeded the application of proportionality as a human rights principle in common law cases. Differences in domestic lawyers’ reactions to proportionality affect the ways in which proportionality deploys its acculturation dynamic in the field of convention rights. In France, the institutional/procedural aspect of proportionality has generally been neglected by domestic lawyers. The employment of proportionality as a European standard in judicial reasoning is residual and accomplishes a rather symbolic function. Since its reception under the HRA, on the contrary, proportionality has systematically served the fulfilment of the UK’s international obligations. Proportionality as a European principle generates an important cultural shift in English public law.